Recently I noticed that I had many duplicate entries in the Open With context menu on my Mac (Mountain Lion). Then after a clean re-install, I noticed the same behaviour repeating. For example, I had three entries for Even Note.
Well, a little googling lead me to this link with this magic command to reset the menu and clean it up.
/System/Library/Frameworks/CoreServices.framework/Frameworks/\ LaunchServices.framework/Support/lsregister -kill -r -domain local \ -domain system -domain user
- This all has to be on one line, but I had to break it up to fit here with the back slash. So to execute, copy it to one line and remove the backslash.
- The location may be different if you are on an older version of OSX per the link above.